My trusty Philips CM8833 has developed an intermittent fault - the picture, which is pretty much perfect, randomly fades to black after using for a while (usually between about 20 minutes and an hour's use).

When the screen fades out, if I peak through the back grill of the monitor, I can see the orange light from the electron gun fades out in time with the picture. If I tap the monitor case, the picture sometimes fades back in briefly, but usually fades out again shortly after...

So loose connection or dry joint perhaps? Any likely places I should check first?